Google Keyword Tool Gone Mad?

I recently did a SEO work for one of my clients and used Google Keyword
Tool to do a keyword research. Only a month ago, that particular keyword
had 6600 global and 4000 local searches.

Now? That same keyword has 870 global and 320 local searches.

Is Google Keyword Tool really gone mad?

Now I'm in trouble because though I put his site in the no. 1 position
within a month time period, he doesn't get a lot of traffic because it
only gets 320 local searches. And I'm not even sure that's close
to the actual searches.